This invention relates to concrete and, more particularly, to fibrous concrete.
Prior art of possible relevance includes U.S. Pat. No. 3,808,085 to Givens, issued Apr. 30, 1974.
Recent years have seen an upsurge in the use of fiber reinforced concrete. Structures formed of fiber reinforced concrete have superior strength over unreinforced concrete and, in many instances, can be employed in lieu of concrete reinforced with reinforcing rods or bars (rebars) to provide similar strength at lesser cost.
Various fibers have been employed. Most often, steel fibers are used, but in many instances, ceramic fibers, such as glass fibers, have been employed. Typically, the fibers are dispersed randomly within the mix and the structure resulting from a pour of the mix. As a consequence, the maximum reinforcement provided by a given number of fibers cannot be achieved. Those fibers parallel to the direction of a bending force application to the concrete structure provide no reinforcing whatsoever, while those fibers only slightly angled with respect to the direction of the bending force application provide but minimal reinforcement. Consequently, it has been necessary to incorporate in such concrete, a far greater number of fibers than actually necessary to ensure that proper reinforcing will be achieved with such a random distribution.
This, in turn, has posed not only an economical problem due to the cost of the increased amount of fibers, but a labor problem as well. When used in the large amounts required, the fibers have a tendency to adhere to each other or "ball." When balls are left in the poured concrete, a weak spot is formed. Moreover, the presence of such balls impedes finishing operations. Accordingly, it has been necessary to manually retrieve the fiber balls from the concrete as it is being poured and finished.